Regenerative repeater



April 26, 1949. L, H RAULT 2,468,556

REGENERAI'IVE REPEA'IER Filed Dec. 2, 1946 2 Shets-Sheet 1 E 2:2: I!- A- 9 Sim I 2 a 4 5 p TIME t MILLISECONDS o 4o I00 I20 (ORIGINAL TRANSMITTED SIGNAL TIME I MILLISECONDS 0 IO 30 50 10 so no (RECEIVED DISTORTED SIGNAL ERIE-a1:

TIME v MILLISECONDS 0 IO 30 5o '70 so no I30 (CORRECTED REGENERATED SIGNAL INVENTOR. JEAN LOUIS HURAULT ATTORNEYS Patented Apr. 26, 1949 UNITED STATE f TENT OFFICE REGENERATIV E EEPEATER .lean Louis l-lurault, Paris, France, assignor to Compagnie Generale dElectricite, Paris,

France, a French corporation Claims.

My invention. relates to high speed telegraphy using codes of the a rhythmic type, and in particular, to means for correcting for line distortion of signal elements, especially their characteristic instants of current reversal.

It is well known, in telesignalling, that the incoming signals, telegraph for example, are deformed with respect to the signals transmitted. This distortion, which depends on the propagation constants of the line, takes the form of a lengthening or a shortening of the signals. In other words, the distribution in time of the characteristics defined by the periods of change of polarity, in the case of operation using double current, is not identical at the sending end and at the receivin end. Moreover, to the distortion of the line there may be added the distortion caused by the transmitter itself.

In order to remedy this disadvantage which may have as a consequence certain errors or omissions in translation, several arrangements have been proposed. These arrangements are, in general, mechanical solutions, the cost of which is high, and which require delicate operating and maintenance apparatus.

A new and particularly simple solution has been described by Pierre, in his patent application Ser. No. 592,770, filed May 9, 1945. It permits of reducing theoretically to Zero and practically to a very small percentage, the distortion of telegraph signals transmitted in an arhythmic or start-stop code, up to agreement with a ratio of distortion of 50%.

In the drawings:

la shows for a typical character the component signal elements constituting a train, in a representative high peed. arhythmic code, as applied by a transmitter at the sending end of a telegraph transmission line;

Fig. 1b shows the received signal train of Fig. 1a after it has been distorted in transmission over a line;

Fig. 1c shows after correction a signal wave train which has been distorted corrected according to a particular method of reversing currentpolarity; and

Fig. 2 is a circuit diagram of the system of the The explanation of the phenomena in the Case of a signal transmitted in the arhythmic or startstop code is as follows: the line is always traversed by a current. This current is positive in the absence or signal modulation. Each character (letter, cipher, punctuation, and so on) is composed of five signal elements called code signals. These signal elements are preceded by a Start signal element (negative polarity) and followed by a Stop signal element. Figure 1a. annexed shows the diagram of a train of signals corresponding to any character taken by way of example.

The receiving relay, which is traversed by positive current in the absence of signal modulation,

is traversed by a negative current during the Start signal, then by positive or negative currents during the code signals, the order and the duration of these signal elements depending on the character sent, and finally, by a positive current during th Stop signal. This latter polarity is maintained until the following train of signal elements of the next character.

The duration of each of the elementary signals is, in the system of practical operation in use on the French telegraph network, 20 milliseconds. The Stop signal may last indefinitely in the absence of signal modulation.

The distortion has for its effect to extend or shorten the signal elements (Start, Code or Stop signals). In other words, if there is taken as zero time the period of passage from the Stop to the Start, the characteristic instants (instants of reversal of current) which, in the case of perfect signal modulation, would have taken place in times of 20-40-80-100 and 120 milliseconds, are advanced or retarded by amounts which depend both on the sending device and on the constant of propagation of the line. Figure 1b represents the wave shape after deformation by distortion in transmission over a line, of the train of signals the perfect signal modulation of which is shown in Figure 1a.

The method forming the subject of the abovementioned invention of Pierre consists in retarding by one half the duration of an elementary signal, that is to say by 10 milliseconds, the characteristic instants of the corrected signal. For this purpose, assuming as origin the reversal Stop-Start times, the times 10-30, --60-70-90- -and milliseconds are noted. These times are the characteristic instants oi the corrected signals. The polarity which follows each new characteristic instant is the polarity of the signal received at the period of this new characteristic instant.

Figure 1c shows the application of this principle to the correction of the distortion which afiected the signals represented in Figure 117.

It is seen that under these conditions the distortion correction may reach 50% on the sole condition that the noting of the time 3050 milliseconds is zmad in .precise manner.

The present'inventionhas for object to provide a device for its carrying out the method which has just been explained.

It is characterised by the use, fort-the notingof the times, of an oscillating relaxation tube the output plate current of whichismornposewof a series of very short impulses spacedapart'bythe duration of an elementary signal of the code used.

The operation of this relaxation tube-'l'isitrige gered by the reception of a Start signal, a mem: ber such as a relay alwaysproviding a certain delay between the appearance of the Stop-Start rever'sal signal element and'the-sending of the first short puls'e. This delayis, preferably, equalto one lialf of-"the duration otan elementary signal of'the code-employed;

A second oscillating relaxation --tubedeliversan 'ou-tputplate current constituted by a series of short'pul-ses-s'paced apart-by the total duration of a j character.

This-second relaxation tube is synchronized by the-first tube,-its first pulse coinciding with the first pulse of this latter. It produces, byits second pulse which is triggered at the end of the last Start signal'element of the character'received, thereturn of the correcting circuits to-the initial state.

'Fligure-arepresents a-construction cf the systemforming-the subject of the present: invention applied to 'a'systemoperatedaccording to a Start- Stopcode-in'which each character is composed of five-elementary signals (plus'a Start signal) each" of these signalelements lasting milliseconds.- The contact representing the rest or de-energized position of "the tongue or armature of each relay is' designated R, and the contact representing its-energized position is designated -'I'.

In this figure -2E=represents the input terminals of the signal modulation to be corrected-as recived onan incoming line and S regeneratedsigna-l'represents the output terminals of"the'cor.- rected'mo'dulation as delivered from the two :out'

put controlled contacts of output relay 'REL-I-"3 towhichtwocontacts the opposite polarities of the-"output linevoltage are applied. as 'a'pplledjtov the out-going line.

The-relay lis the starting relay and'has -twowindings. During-the Stopsignal element this relay=l=is at rest in the position R on its contact ll: its first winding can' be traversed only by the negative telegraph currents, by reason of the presence inits circuit of'the rectifying element:

of-unilateral conductivity red; on the other hand; its second winding is traversed by the" plate current-of the tube L2, which isthen zero, since the-'cathodesof'the tubes Ll and-L2 are 'not grounded'when the-relay= RELI is on its rest" contacfiR- or- I I:

The relay-2 is the end relay and'has three wind,-

ings. "Its three tongues-are normally in the position'Rlrestl on contacts 22, 24; ztexcept during" the-duration of the second pulseof the oscillat ing relaxation tube L2. The function of these contacts of relay 2 is to bring to an initial defined state the potential of the condensers C1, C2 and C3, and the electromagnetic energy contained in the relay I. The precision of the determination of the characteristic instants of the corrected signal element depends on the reactive energy of the circuit elements which determine the frequency of the oscillators. It is important that at the moment of Stop-Start reversal, this energy may be perfectly defined.

Therelayit which hasetWQWiIldi-hgs is responsive toth'e pulses of the plate current of 'the tube Ll (20 milliseconds oscillator). The pulses throw the tongue of the relay 3, either to the left to con- ---tact 3:l ,-o1=tothe right to contact 32, according to the position of the armature of relay 4, Which followslthe variations of the applied signal re- -'ceived-at input. terminals E. Relays 3 and 4 are'usual types-of'telegraph relays with polarized armatures; and when their armatures have been actuated against one contact by a current applyverse; Current flows. in a one or: the other. of! the; windings of relay: 3sto%throwits armature: one.

way or the other. Currentmayflowm-in either direotionthroughwthe winding. of thearelay 4. 1 The line sending battery Msapplies togthe output terminal s :either a; positive line potential through.

3 contact 3l ora negativezline potentialkthrough contact 32;.

The tube aLI is-the oscillating relaxation tube of' period '20 milliseconds. oscillationzis determined by the circuitiZz C2.

external synchronization: may be applied to thisjube through. the. medium ,of the transe former :as from a source-6 I: supplying 50 'cycle alternating current. The :source ot-synchronizati'on may; moreover; be common to a-I-large number of i correctingadevices;

- Il ie-"tub'ezLzv is the. oscillating relaxation tube M5120:milliseconds period; 'The. frequencyof this.

oscillation 'is determinedrby the circuit Z: C3. Thezreleaiseof the top produced by. the tube -L2 is synchronised with the release-ofthesixth-topof thertube Li due to thetransformer-Xn The apparatus operates: in the followingmanner. 10 milliseconds after the Stop-Startreversal, the relay Lstarts operating; the cathodes of the tubes: In and'L'z. are re -connected to earth;

the tube L1, the i circuits of which have; been. designed for thispurpose; mark the times 10-30- 50-70-90-110 and milliseconds, byvshortcurrent pulses in its plate circuit. Thesepulses -give the characteristic instants a of the corrected sigand duringia' very shortrt'ime' brings-the tongues of the relay 2 to their actuated or working 'posi-- tion. I Thisslastsoperationproduces' the discharge of; the condensers Ci; Car-and; (bras also; the -.interruption' ofl-currentzinithe winding. lsofs the relayrl Immediately aftenthe-endiof- :the; pulse of The frequencyof ithis.

the tube 2, the circuits return to their initial state, and are ready to effect a new correction, the commencement of which will be controlled by a Stop- Start reversal.

The operating cycle for one given complete start-stop signal is as follows:

Time: Rest position-Signal stop:

Positive polarity on the right terminal E.

The winding I of relay I is not energized because of the presence of the rectifier. Its winding 2 is not energized since the circuit of the tube L2 is open because of the release of relay l.

t The relay I, therefore, remains in rest posiion.

The winding I of the relay 2 is permanently energized, and tends to place the armature of this relay in the rest position, its winding 2 is energized by the current of the stop signal and its action is opposed to that of the winding I, but the flux of winding 2 is smaller than that of winding I. Furthermore, the winding 3' is not energized since the circuit of the tube L2 is open to ground because of the rest position of relay l.

The relay 2 remains at rest.

The relay 4 is energized in the sense corresponding to the positive impulses and it directs the +A voltage toward one of the windings of relay 3 (I for example). However, this winding is not energized, since the tube LI does not deliver output but the armature of relay 3 stays, however, on its contact +T, where it has been placed at the beginning of the stop signal, and a positive polarity is sent and applied to the right terminal X.

Time: Zero.Beginning of the start signal-The polarity of the right terminal E becomes negative:

The winding I of relay l is energized but relay I remains at rest because of its delayed operation. The winding 2 of the relay I is not excited, its circuit being opened by the rest contact of relay l.

The winding 2 of relay 2 is energized in the sense inverse to the preceding sense and its flux reinforces that of winding I, to maintain the armature at rest, the winding 3 is not energized.

The relay 2 remains at rest.

The relay 4 is energized in the opposite sense from the preceding sense; it puts into the circuit the winding 2 of the relay 3, but this winding is not yet energized since the circuit of the tube LI is opened by the rest position of relay I. The armature of the relay 3, therefore, does not budge and a continuous positive polarity has been applied to the terminal S.

10 milliseconds-Midpoint of the start signal:

The delay action period of relay I having expired, the relay I comes into operative position. It closes a circuit of the tubes LI and L2 which produce a very short pulse. The winding 2 of relay I is energized during the duration of the short pulse, which has no efiect on relay I, the ampere turns of the winding I being preponderant.

The winding 3 of the relay 2 is energized during the duration of the short pulse, which tends to hold its armature in operative position, but the ampere turns of this winding are smaller than the sum of the ampere turns of the windings I and 2, so that the relay 2 remains in unoperated position.

20 milliseconds:

It is the theoretical instant of the beginning of the first characteristic element, but no modification of the received current is yet produced because of the delay of the distortion.

1. The polarity of the first characteristic signal is negative 15 (24 milliseconds for example, supposing a delay of distortion of 4 milliseconds) .The first characteristic element is efiectively received at E:

The relay I continues to be excited by its winding I and remains in operated position. No change is produced for the relay 2, which remains in rest position. The relay 4 does not budge and the relay 3 continues to send to terminal S a negative polarity.

30 milliseconds-Midpoint of the first characteristic element:

The winding I of the relay I continues to be energized, and the relay I remains in operated position.

The winding 2 of the relay I is not energized since the tube L2 does not oscillate, the frequency of its oscillations being equal to 120 milliseconds.

The winding 3 of the relay 2 is not energized for the same reason and the relay 2 remains in unenergized position as during the starting operation.

The tube LI produces its second short pulse, the frequency of its oscillation being adjusted to 20 milliseconds. The relay 4 is energized in the same sense as during the starting period and does not budge.

The winding 2 of the relay 3 is energized during the duration of the short pulse produced by the tube L! which retains relay 3 in its position T.

A negative polarity continues to be sent to terminal B.

2. The polarity of the first characteristic signal is positive (24 milliseconds for example, assuming a delay 0 f distortion of 4 milliseconds) .The first characteristic element is effectively received at E:

The winding I of the relay I ceases to be energized, its Winding 2 is no longer energized, and the relay i remains in operative position.

The armature of the relay 4 swings onto its other contact putting into circuit the winding l of relay 3, but this winding is not again energized, since there does not still exist the instant of the duration of the short pulse of the tube LI.

The armature of relay 3, therefore, stays on the contact -T and a negative polarity is always applied to the terminal S.

30 milliseconds.Midpoint of the first characteristic element:

The windings I and 2 of the relay I are not energized, the relay remains in operated position, the relay 2 remains in unenergized position, no modification occurring in its supply circuit.

The tube LI produces a second short pulse during the period in which the winding l of the relay 3 is energized, the relay 4 remaining inthe ssame position". :The armature relay 3 swings, sending aipositive polarity-to terminal S.

20 milliseconds.-Theoreticaltime.of the beginning of 1 the =Stp signal:

(126 milliseconds for'example, supposing that the distortion delay is 6 milliseconds).-Beginning of the stop signal:

The polarity at the'input becomes positive, the=winding I Qf-therelay I continues to not be, or ceasestoibe, energized, according to the polarity of the preceding signal, but the relay I atall events remains in energized position.

The relay 4 puts or'maintains in a circuit the winding I of the relayv 3', but this winding is not energized, since the oscillator tube Ll is not oscillating, 'so that the-armature of the relay 3' stays in the position in which it was before.

130 mz'ZZiseconds.-The tubes -LI and L2 each produce a pulse:

Across the tube L2 the winding 2 of relay I and the windingil of; relay 2 are energized during the duration ,of .theshort pulse.

The winding 3 oflthe relay 2 puts the relay 2 into operated position since=the-winding 2 of this relay is at that time traversed by a positive-current which, likewise, tends-t0 place the armature in operated position; the two windings'Z and 3 act inithe same sense and their action involves-that-of the winding I; the energization of the winding IV of relay I being interrupted, this relay immediately goes back to unenergized positionbecause of the efiect of its winding 2, the other contacts-of relay 2 short circuit the shunted condensers R202 and R303.

Furthermore, the winding I of relay 3 is energized during the duration of the short pulse of the tube LI and the armature of 3 passes, or remains, on the positive terminal, applying apositive polarity to the terminal S.

At the end of the short pulse, the-winding 3 of-relay-2 ceasesto be *energized and relay 2 returns tothe rest position under the action of its winding I which -ispreponderant with relation to the winding 2.

The winding 2 of the relay-l likewise ceases to be energized, the relay I does notbudge and remains .in rest position.

The relay 4 remains energized in the sense which corresponds to'putting into circuit of the winding I of relay'3.

All the members are-then restored to their initial. state.

Thedevice just described by way of example is intended to operate with a given particular code and agiven defined'duration of signals. It is obviousthat without departing from the scope of the present invention, such a device would permit of correcting an arhythmic telegraphic operation of any speed and code.

I claim:

1. A signal correcting device for a start-stop telegraph system comprising two input terminals to which are applied'the distorted transmitted signal impulses which are'to beregenerated, a source of continuous current, a first telegraph relay, a second. double winding relay, said first relay being connecte'd'to be actuated'by said received impulses, said second relay having two controlled "contacts, said first relay being connected to connect with one pole of said source of continuous current, one terminal selectively of either one of the two opposing windings of said second relay according to the polarity of the receivedimpulses which are-:appliedto the 8 winding: of said first relay, a. pairvof output-terminals, said second relay being connected toiap- Fly to one of the said output terminalsa-positive or negative voltage according to thelposi- .tion of it armature, a relaxation oscillator tube arranged to produce spaced short pulses .of the predetermined assigned duration of a signal element of the code being used, the other terminal in common of the two windings of'said secondrelay being connected to the other pole of said source of continuous current through the output and input terminals of said tube.

2. A device according to claim 1, characterized bythe fact that for the purpose of causing the triggering of the first pulse of the relaxation oscillator tube at the-midpoint'of the. theoretical duration of the start signal element of each code character, it comprises a third starting relay, a rectifier connected to allow to pass only the currents whose polarity corresponds to the start signal element, one of the windings oi said'thirdrelay being connected to the signal input terminals through said rectifier, the third relay being connected for closing the cathode circuit of said relaxation oscillator tube, the said third relay being retarded by an interval equal to half of the theoretrical duration of a signal element or the code employed.

3. A signal correcting device for a start-stop telegraph system comprising two input terminals to which are applied the distorted transmitted signal impulses which are to be regenerated, "a source of continuou current, a first telegraphrelay, a second double Winding relay, said first relay being connected to be actuated by said received impulses, said second relay having'two controlled contacts, said first relay being-connected to connect with one poleof said source of. continuous current, one terminal selectively of either one of the two opposing windings .of said second relay according to the polarity ofthe received impulses which are applied to the winding of said first relay, a pair of output'terminals, said second relay being connected to, apply to one of the said output terminals a positive or negative voltage according totheposition of; its armature, a relaxation oscillator tube arranged to produce spaced short pulses of the predetermined assigned duration of a signal element of the code being used, the other terminal incommon of the two windings of saidsecondrelay being connected to theother pole. of said source of continuous current through the output and in,- put terminals of said tube, said device further comprising a secondtube arranged as. a relaxation oscillator .and adjusted in such. manner .as to give spaced short pulses of the theoretrical duration in the code employed of a complete character, a third starting relay having two windings, a fourth terminal relay, a plurality of ,,condensers arranged for providing delay of the starting. relay and the starting intooscillation. of said second tube, the plate circuit of the saidsecon'd tube being connected to energize on the one hand a second winding of said third starting relay whichproduces a. flux opposed to that due to. its first winding, and also being connected toenergize a winding of said fourth terminal, relay, said fourthterminal relay being connectedlto shortcircuit the saidv condensers.

4. A device according to claim 3, characterized by the. fact that for thepurpose ,of causin theinitiation of the first pulse of said-second relaxation oscillator tube at the sameinstant as that of the said first relaxation .oscillatortube.

9 the cathode circuit of said second relaxation oscillator tube is closed through the same said third relay which also controls the cathode circuit of said first relaxation oscillator tube.

5. A device according to claim 3, characterized by the fact that for the purpose of avoiding having the first pulse of the second relaxation oscillator tube cause the operation of said fourth terminal relay, the said fourth relay comprises, besides its winding traversed by the output current of the said second oscillator tube, two other windings, one of which is connected to be permanently energized by a source of continuous current and the other winding of which is connected to be energized by the impulses of the received signal element received on said input terminals, the ampere-turns in each one of these three last said windings of said fourth relay being designed in such manner that the flux of the winding traversed by the output current of said second tube can only cause the operation of said 10 fourth relay when its said winding which is energized by the impulses of the signals received on said input terminals is traversed by a current of the sense corresponding to that of the stop signal, and that the flux of said last mentioned winding can cause the operation of said fourth relay whatever may be the sense of the impulse of the received signal current.

JEAN LOUIS HURAULT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,133,456 Kinkead Oct. 16, 1938 2,357,840 Martin Sept. 12, 1944 2,406,096 Morrison Aug. 20, 1946 

